L. Charles Burgwardt wrote:
>
> I'm looking for a perimeter measurement routine written in IDL. I have a
>
> binary image. The output could be in any units such as pixel perimeter,
> crack perimeter, or line segment. A boundary following routine would be
> good also, ie ordered list of boundary pixels.
>
> Charlie Burgwardt
I attached a little "boundary crawler" routine that I used to get the
outline polygons for individual countries after creating maps with
/continents. Subroutine getpoly does the actual job. It's nothing too
sophisticated and may not be the utmost efficient routine, but it worked
very stable (at least for reasonable choices of starting points). You
need
to give the routine one point that is within the region you want to
circumvent. It will then move north to find the boundary, then crawl
clockwise until it reaches a point that was already marked. Should be
fairly
straightforward to adapt for different threshold values or ranges.
Hope this helps,
Martin.
--
------------------------------------------------------------ -------
Dr. Martin Schultz
Department for Engineering&Applied Sciences, Harvard University
109 Pierce Hall, 29 Oxford St., Cambridge, MA-02138, USA
phone: (617)-496-8318
fax : (617)-495-4551
e-mail: mgs@io.harvard.edu
Internet-homepage: http://www-as.harvard.edu/people/staff/mgs/
------------------------------------------------------------ -------
; ======== HELPER ROUTINES FOR FILLIT =================
function testpix,im,i,j
test = intarr(4)
test(0) = im(i+1,j) gt 0 ; east
test(1) = im(i,j-1) gt 0 ; south
test(2) = im(i-1,j) gt 0 ; west
test(3) = im(i,j+1) gt 0 ; north
return,test
end
function evalpix,im,i,j,direction
test = testpix(im,i,j) ; get neighbouring pixel values
eval = (5 + direction - indgen(4)) mod 4 + 1 ; evaluation mask
eval = eval*test ; blank out zero values
minval = min(eval(where(eval gt 0)))
newdir = where(eval eq minval)
; print,direction,byte(eval),minval,newdir(0),format='(i2,":",6i4)'
return,newdir(0)
end
; GETPOLY : automatic generation of country boundaries
pro getpoly,im,i,j,x,y,XOFF=xoff,YOFF=yoff
if (n_elements(XOFF) eq 0) then xoff = 0
if (n_elements(YOFF) eq 0) then yoff = 0
if (im(i-xoff,j-yoff) ge 1) then stop,'Already on boundary.'
while (im(i-xoff,j-yoff) lt 1) do begin
j = j+1 ; search for boundary
endwhile
; save i,j pair
i0 = i-xoff
j0 = j-yoff
; initialize x and y and direction
x = i0
y = j0
im(i-xoff,j-yoff) = 2
dir = 0 ; 0=E, 1=S, 2=W, 3=N
steps = 0L
; crawl along boundary
repeat begin
if (steps mod 200 eq 0) then tv,im
; test if pixel at right is boundary, if not, test pixel straight
; ahead, then pixel at left, finally move back
res = evalpix(im,i-xoff,j-yoff,dir)
case res of
-1 : print,'**'
0 : i = i+1 ; east
1 : j = j-1 ; south
2 : i = i-1 ; west
3 : j = j+1 ; north
endcase
x = [ x, i-xoff ]
y = [ y, j-yoff ]
steps = steps+1
dir = res
im(i-xoff,j-yoff) = 2
endrep until ((i-xoff eq i0 AND j-yoff eq j0) OR steps ge 20000)
tv,im ; final display
print,steps ,' used for boundary definition.'
return
end
pro ind2xy,index,x,y,xsize=xsize
if (n_elements(xsize) eq 0) then xsize = 720
x = (index mod xsize)
y = fix(index/xsize)
return
end
; =========== PICKLIST ROUTINE =========================
;
; interactive picking of country coordinates with mouse
pro picklist,filename,SCALE=SCALE,start=start,XOFF=xoff,YOFF=yof f, $
exclude=exclude
if (n_elements(xoff) eq 0) then xoff = 0
if (n_elements(yoff) eq 0) then yoff = 0
if (n_elements(exclude) eq 0) then exclude = 0
if (n_elements(start) eq 0) then start = 0L
if (n_elements(SCALE) eq 0) then SCALE = 1
ascale = float(SCALE)
; create two files interactively :
; a country file with starting points for each country
; a name file with country numbers and names
openw,ilun,filename+'.dat',/get_lun
printf,ilun,'COUNTRY X Y'
openw,olun,filename+'.names',/get_lun
; use CURSOR to pick points
print,'left click : the last point defining a country or an exclusion'
print,'middle click : not the last point ... (e.g .for islands)'
print,'right click : no more input (does not produce an entry !)'
print
mx=0 & my=0
status = -1
count = long(start) ; country counter
cname = ''
read,cname,prompt='COUNTRY : '
printf,olun,count,cname,format='(i4,1X,A)'
while (status ne 4) do begin
print,count,cname,format='(i4,A)'
cursor,mx,my,/down,/device
status = !err
if (status lt 4) then $
printf,ilun,count,mx/ascale+xoff,my/ascale+yoff, $
format='(i6,2f10.3)'
if (status eq 1) then begin
count = count + 1
read,cname,prompt='COUNTRY : '
if (cname eq '') then begin
close,/all
return
endif
printf,olun,count,cname,format='(i4,1X,A)'
endif
endwhile
close,/all
return
end
; ============== COUNTRIES : MAIN PROGRAM =====================
;
; requires GIF files with "empty" country outlines as generated
; by continents.pro
;
; COUNTRIES operates in 3 steps:
; - interactive determination of country coordinates and country names
; - automatic determination of country boundaries
; - merging of "filled" continent images and aggregating
;
; typical calling sequence:
; countries,continent="northamerica",start=1
; countries,continent="southamerica",start=15
; countries,continent="europe",start=28
; countries,continent="asia",start=67
; countries,continent="australia",start=89
; countries,continent="africa",start=94
;
; countries,continent="northamerica",/fillit
; countries,continent="southamerica",/fillit
; countries,continent="europe",/fillit
; countries,continent="asia",/fillit
; countries,continent="australia",/fillit
; countries,continent="africa",/fillit
;
; countries,/merge
;
pro countries,continent=continent,start=start,fillit=fillit,excl ude=exclude, $
merge=merge
; create region -> grid maps and country -> grid maps
; NEW version : uses pre-stored GIF images for country boundaries
SCALE = 8 ; 2 makes it a 0.5x0.5 grid, 4 gives better resolution
; SCALE must be identical to that used in CONTINENTS.PRO !!
; for simplicity, the window size is the same for all continents, only
; the offset shifts - always draw complete map into pixmap but then copy
; only continent region
XOFF = 0 & YOFF = 0
if (n_elements(continent) eq 0) then continent = "northamerica"
continent = strlowcase(continent)
; for merge option: define continent names as array and create loop
; other calls willloop only once
if (keyword_set(merge)) then begin
cnnames = [ 'northamerica', 'southamerica', 'europe', 'asia', $
'australia', 'africa' ]
ic0 = 0
ic1 = 5
grandim = intarr(SCALE*360,SCALE*180) ; result image array
endif else begin
ic0 = 0
ic1 = 0
endelse
for ic = ic0,ic1 do begin
; IMPORTANT : the following offsets must be identical with those
; given in CONTINENTS.PRO !!!
if (keyword_set(merge)) then continent = cnnames(ic)
case continent of
"northamerica" : begin
XOFF = 0
YOFF = 90
end
"southamerica" : begin
XOFF = 45
YOFF = 20
end
"africa" : begin
XOFF = 120
YOFF = 50
end
"europe" : begin
XOFF = 90
YOFF = 90
end
"asia" : begin
XOFF = 225
YOFF = 90
end
"australia" : begin
XOFF = 225
YOFF = 30
end
else : message,'invalid continent !'
endcase
XSIZE = 135
YSIZE = 90 ; plot size in degrees (multiply by SCALE)
; make sure that complete plotting area is used
!p.position=[0,0,1,1]
if (not keyword_set(merge)) then goto,no_merge
; ------ MERGING SECTION -------------------------------------
; read in image with filled continents
read_gif,continent+'.gif',im
; convert all non-white, non-country pixels to white
ind = where(im lt 3)
if (ind(0) ge 0) then im(ind) = 0
print,ic,' : ',max(im)
; add partial image to total image
grandim(SCALE*XOFF:SCALE*(XOFF+XSIZE)-1,SCALE*YOFF:SCALE*(YO FF+YSIZE)-1) = $
grandim(SCALE*XOFF:SCALE*(XOFF+XSIZE)-1,SCALE*YOFF:SCALE*(YO FF+YSIZE)-1) + $
fix(im)
endfor ; ic loop for merge
print,'grandim:',max(grandim)
; load new color table
loadct,27,bottom=1
tvlct,r,g,b,/get
if (!D.n_colors lt 170) then print,'WARNING : not enough colors !'
; write complete image as gif file
write_gif,'world_countries_large.gif',byte(grandim),r,g,b
; condense image by aggregating 4x4 pixels
; this gives 0.5x0.5 degree resolution
; NOTE: tried rebin before, but this leads to unpleasant white lines
; therefore have to go through each 4x4 block
tmp = intarr(720,360)
rescale = fix(SCALE/2)
print,'Condensing image ... please be patient!'
for i=0,719 do begin
for j=0,359 do begin
block = grandim(i*rescale:(i+1)*rescale-1,j*rescale:(j+1)*rescale-1)
code = 0
if (max(block) gt 0) then begin ; found a country
; determine country code with maximum portion
u = block(uniq(block,sort(block)))
u = u(where(u gt 0))
for n=0,n_elements(u)-1 do begin
testind = where(block eq u(n),count)
if count gt code then code = u(n)
endfor
endif ; else only water
tmp(i,j) = code
endfor
if ((i mod 36) eq 0) then tv,tmp
endfor
; shift by 10 degrees west in order to start at -180
newim = [ tmp(700:719,*), tmp(0:699,*) ]
; move all colors down 3 so that first country starts at 1
ind = where(newim gt 2)
newim(ind) = newim(ind)-3
print,max(newim)
tv,newim
write_gif,'world.countries.gif',byte(newim),r,g,b
return
; ------------------------------------------------------------ ------
no_merge:
; load continent
read_gif,continent+'.empty.gif',im
ind = where(im gt 0)
if (ind(0) ge 0) then im(ind) = 1
; open a display window and show map
window,xsize=XSIZE*SCALE,ysize=YSIZE*SCALE
curwin = !d.window
tv,im
if (keyword_set(fillit)) then goto,fillit
; create picklist
if (keyword_set(exclude)) then $
picklist,strlowcase(continent)+'.exclude',scale=SCALE, $
XOFF=xoff,YOFF=yoff,/EXCLUDE $
else $
picklist,strlowcase(continent)+'.countries',scale=SCALE, $
start=start,XOFF=xoff, YOFF=yoff
return
fillit:
; draw black frame around image
s = size(im)
im(0:1,*) = 1
im(s(1)-2:s(1)-1,*)=1
im(*,0:1) = 1
im(*,s(2)-2:s(2)-1) = 1
readdata,strlowcase(continent)+'.countries.dat',data,cols=3, $
/noheader,skp1=1
c_col = reform(data(0,*))
iind = reform(data(1,*))
jind = reform(data(2,*))
if (n_elements(start) eq 0) then start = 0
for i = 0,n_elements(iind)-1 do begin
if (c_col(i) ge start) then begin
getpoly,im,fix(iind(i)*SCALE),fix(jind(i)*SCALE),x,y, $
xoff=xoff*SCALE,yoff=yoff*SCALE
; and display manipulated image
tv,im
polyfill,x,y,/device,/fill,color=c_col(i)+3
im = tvrd() ; read image with filled continents from display
endif
endfor
; save full resolution image as bytemap (use write_gif)
write_gif,strlowcase(continent)+'.gif',im
; save map
; openw,olun,'mapimage.txt',/get_lun
; for i=180*SCALE-1,0,-1 do $
; printf,olun,im(*,i),format='(360*SCALE(i1))'
; close,/all
return
end
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